Electric selective system



ELECTRIC SELECTIVE SYSTEM Filed July 11, 1935 I NVEN TOR HORACE EDGARI-WPHRIES ATTY Patented July 20, 1937 UNITED STATES PATENT CFFIQEEngland, assignor to Siemens Brothers &

Company Limited, London, England Application July 11, 1935, Serial No.30,819 In Great Britain August 18, 1934 8 Claims.

This invention relates to electric selective systems and has in viewimproved arrangements for the determination, by an outgoing or selectingcircuit of the nature of an incoming or selected 5 circuit to whichlatter the former may have become connected. It is useful in those casesin which a selecting device is required to bring about differentoperations or itself to operate in different manners according to thenature of the in- 10 coming circuit to which it may have becomeconnected.

The terms outgoing and incoming are used for convenience and imply,respectively, where the context permits or requires, any suitable active15 circuit which is adapted to become connected with any suitablepassive circuit.

In one aspect of the invention, the determination of the nature of anincoming circuit is efiected by arranging that of two apparatus, one

20 in the outgoing circuit and one in the incoming circuit, the order oftheir operation shall depend upon the nature of the incoming circuit.The two apparatus may conveniently consist of relays.

In another aspect of the invention, the deter- 25 mination of the natureof the incoming circuit is eiiected by arranging that the time,relatively to the time at which an apparatus in the outgoing circuitoperates, at which a signal is transmitted from the incoming circuit tothe outgoing 30 circuit shall be characteristic of the nature of theincoming circuit. The signal, if transmitted in time, will be detectedby an apparatus, which may be a relay, and, moreover, may be a highspeed relay of the type disclosed in the patent of Ernest 35 J. Gaohet,No. 1,992,619, granted Feb. 26, 1935. If

the signal is not transmitted in time, the operation of the apparatus inthe outgoing circuit will have proceeded to such a stage that detectionof the signal may be prevented, or that the 40 efiect of its detectionmay be annulled.

In certain applications of the invention, as for instance, itsapplication to the telephone art, the determination of the nature of theincoming circult (which may be a subscribers line) is con- 45 venientlyeffected at the time at which the incoming circuit is taken intoengagement by the outgoing ci cuit (which may be the final selectorswitch seizing the line), and, in such applications, the sensitiveapparatus may be the relay which 5 is used to test the idle or busycondition of the incoming circuit and the signal may be transmitted overthe conductor over which that test is made. The apparatus in theincoming circuit may then be a relay in the test circuit and the 55 diifering natures of the incoming circuits may be indicated by relays whichrequire differing times for their operation. The invention will bedescribed in connection with a system having these characteristics and,moreover, in connection with an automatic telephone system.

Further exemplary description may more con veniently be given with theaid of a diagram. Reference is therefore made to the accompanyingdrawing which shows certain parts of a final selector in a known systemof automatic telephony and. which illustrates the invention, the finalselector may be of the general type shown in British Patent No. 412,722,accepted July 5, 1931.

In the system of automatic telephony to which the invention is regardedas being applied, the setting of a final selector to the contacts of asubscribers line is effected under the control of an apparatus common toa number of final selectors which registers impulses characteristic ofthe line (but not of the nature of the line) into association with whichthe final selector is eventually to be brought, effects an electricalmarking of a contact appropriate to the said line, and initiates andterminates a. selective operation on the part of the final selector tobring the final selector into association with and to prevent itsoverrunning the said appropriate contact.

In the diagram, the apparatus indicated above the chain line is to beregarded as part of the final selector and of the exchange end of asubscribers line circuit, and that below the chain line is to beregarded as part of the common controlling apparatus. The final selectorand common control apparatus are the outgoing, and the subscribers linecircuit is the incoming circuit. Only those parts of these elementswhich are necessary to the understanding of the invention are shown.

It may be assumed that the common control apparatus becomes temporarilyassociated with the final selector upon the operation of a relay, notshown, but represented by three of its contacts kl to 703, that upon thecompletion of the reception, by the common control apparatus, ofimpulses representing a wanted line the switch indicated as MS willoccupy a position indicative of the position to which the final selectorshall move, that to this latter end the several contacts in the bank ofswitch MS are appropriately crossconnected to contacts in the bank G ofthe final selector, that the idle or busy condition of a wanted line isindicated by the potential applied to its contact in the bank P the idlecondition being indicated by low resistance battery applied 5 to thatcontact, that the marking and test wires (mw and raw) of a line areconnected to corresponding contacts in the twobanks G and P, and thatthe wipers which engage these two banks move synchronously.

It may further be assumed that during the reception by the commoncontrol apparatus of the final train of impulses indicative of a Wantedline, the three relays, not shown, represented respectively by theircontacts bi, cl and c2, and fl and f2 are operated so that the contactsoccupy their positions alternative to those shown, that upon thecompletion of the reception of the final train of impulses the relayrepresented by its contacts cl, c2 releases so that these contactsoccupy the positions shown, that the relays represented by contacts hiand ft, ]2 remain operated, that, due to the simultaneous operationduring the reception of impulses of the relays represented by contactsii and c! a circuit is completed through winding (1) of relay U, andthat when connection is established, relay H operates and at contact hlcloses a holding circuit.

Upon the completed reception of the final train of impulses indicativeof the wanted line, and upon the consequential release of the relayrepresented by contacts cl andcZ, a circuit is completed from earth, byway of contacts tl, fl, tal, cl, and ul, low resistance winding (II) ofrelay U, contacts 02 and kl, and winding L of a latch magnet to battery.The latch magnet serves, upon operation, to remove a latch from themoving parts of the final selector and to close a circuit for a drivingmotor as may be understood or I as is'known in the art of automatictelephony.

As a result of the closing of the above circuit relay U is heldoperated, relay TA is short circuited, the latch magnet is operated, andthe final selector is driven in its search for the wanted line. As soonas the two wipers which respectivly serve the two banks G and Pencounter the contacts of the wanted line, a circuit becomes completedfrom earth, through rectifier R, windings of high speed relay T, wiperand contact of marking switch MS, contact and wiper G of the finalselector, contact k2, wiper and contact p of the final selector, andwinding of the cut-off relay CO shunted by contact col and resistanceOR, to battery. In this circuit both relay T and relay 00 will operate,but the former, which has an operating speed of the order of onemillisecond, will operate very much more quickly, in terms of the timesof operation of relays, than will the latter. Relay T, at its contacttl, opens the circuit of the latch magnet L and of high speed relay U,both of which release and the former of which arrests the motion of thefinal selector.

When relay CO does operate, the impedance in the circuit of relay T is,owing to the removal of the shunt constituted by resistance CR fromacross the winding of relay CO, temporarily increased to such an extentthat relay T cannot or may not hold. When the impedance in the circuitof relay T falls sufficiently, relay T, if it shall have released, willagain operate.

The operations described above, except insofar as they involve relay U,relay TA, and the temporary release of relay T are those usual, underthe conditions described, in a known system of automatic telephony.

At the moment at which relay T originally operated, that is, before itstemporary release, the short circuit was removed from across relay TA anoperating circuit for which therefore then existed from earth, by way ofcontact f2, 02, kl, and latch magnet L to battery. Relay TA, but notmagnet L operates in this circuit. The method of operating relay TA isimmaterial to the invention and the method described is not claimedherein.

At the moment at which relay U released, following the operation ofrelay T and before its temporary release, and moreover before relay TAshall have operated in the circuit described in the preceding paragraph,a circuit, at present open at contact tl, is prepared from earth, by wayof contacts tl, fl, tai, cl, ul, winding (I) of relay V, to battery, forrelay V. Whether or not this circuit shall be completed, that is whetheror not relay V shall be given an opportunity to operate, will dependupon whether contact tl shall fall back, upon the temporary release ofrelay T, before contact tal shall have had time to open the circuit orshall, if it fall back at all, fall back after that event. Relay Vshould preferably be a high speed relay.

For the purpose of the invention in the example of circuit underdescription, it is arranged that the speed of operation of relay TAremains constant, since this relay is associated with the activeoutgoing circuit, but that the speeds of operation of different relaysCO, associated with diiferent sorts of incoming circuits, the differencebetween which circuits it is desired that the outgoing circuit shalldetermine, are diiferent. It has to be observed that the difference inthe speeds of operation has to be such that, in some cases the relay COconcerned has to operate and relay T has to fall off before relay TAshall have operated so that relay V may operate, Whilst in other casesthe relay CO concerned has to operate so late with reference to the timeat which relay TA operates that relay T, if it releases at all, isunable to complete the circuit of relay V so that this latter relay maynot operate. Thus, in the example under description, the nature ofincoming circuit with which the outgoing circuit has become connected isregistered by the condition (operated or unoperated) of relay V which,at its contact 'vl closes a holding circuit for itself and at itscontact 212 may cause appropriate or prevent inappropriate operations.

Adjustment of the speeds at which different relays 00 associated withdifferent subscribers Q lines operate may be eifected by providing thedifferent relays with alternative windings one producing a heavy and theother a light flux.

It remains to be observed that, in the system of automatic telephony inconnection with which it s has been found convenient to describe theinvention, the normal immediate method of preventing intrusion, by asecond final selector, upon a line which is already engaged by a firstfinal selector,

is by connecting earth, from contact tl, through the comparatively lowresistance winding (I) of relay T, to the contact in banks G and P ofthe wanted line, so that the potential thereon is brought so near toearth potential that a second relay T associated with the second finalselector the contacts of which are multipled to those of that shown, isunable to operate to arrest the motion of the second final selector; andthat there is a period, during the temporary release of relay T, whenthis low resistance earth is not applied. Intrusion is, however, nonethe less prevented during the time that relay T is released for, as willbe appreciated, as it was the increased impedance upon the operation ofrelay CO in the circuit of relay T which brought about the temporaryrelease of relay T, so that the same increased impedance will prohibitthe operation of a second relay T. Even should the second relay Tassociated with the second final selector be applied to the multipledcontact at the moment when the impedance in the circuit of the relay Tshown shall have adjusted itself to that Value at which the shown relayT can operate, the second relay T will not operate because it will, onaccount of the great speed at which the second final selector passes offthe contact, be applied to the said multipled contact for aninsufiicient time. The difference between the conditions which obtainwhen the second relay T might be applied at the moment mentioned in thepreceding sentence and which prohibit the operation of the said secondrelay, and those which obtained when the first relay T was applied andwhich did not prohibit the operation of the said first relay althoughthe durations of their respective applications are, so far as may be,the same, is that, in the case of the application of the second relay T,relay CO is not, whereas in the case of the application of the firstrelay T it is, shunted by the resistance CR.

The use of a rectifier in series with relay T forms no part of theinvention and is not claimed herein.

Storage means may be provided whereby a plurality of signals may bereceived for discriminating between a plurality of difierent incomingcircuits. For instance, by arranging contact tai' as a change overcontact and by associating a relay similar to relay V with the frontcontact tel, the nature of both of two incoming circuits can bepositively registered. In this case the second relay V would be guardedby a contact on relay V so that it should not operate when, eventualiy,relay T releases.

I claim:-

1. In a selective signaling system, a plurality of incoming circuits, aconnecting circuit having 1 -eans for testing said incoming circuits anddetermining the condition thereof, said testing means including anapparatus in the incoming circuit and another in the connecting circuit,the condition of the incoming circuit determining the sequence ofoperation of the apparatus in the incoming circuit and that in theconnecting circuit, and means in the connecting circuit controlled bythe sequence of operation of said apparatus.

2. In an electric selective system, a plurality of incoming circuitscapable of having different conditions existing therein, an outgoingcircuit having means for connecting with and testing said incomingcircuits, said testing means including a test element, said test elementoperating within a predetermined time after connecting with an incomingline if one condition exists thereon to indicate that condition andindicating another condition if not operated within that predeterminedtime.

3. In an electric selective system, an outgoing circuit, a plurality ofincoming circuits of different natures, means for connecting outgoingcircuits with said incoming circuits for testing, means in the incomingcircuits for sending a signal back to the outgoing circuit atpredetermined times dependent upon the nature of the incoming circuit,and means in the outgoing circuits for determining the nature of theincoming circuit dependent upon the time after seizure when said signalis sent back.

4. In an electric selective system in which an outgoing circuit isadapted to be connected with incoming circuits of different natures,testing device in the outgoing circuit having means operated in onemanner when an incoming circuit is connected with, other meanscontrolled by said first means, said first means then operated inanother manner either before or after the said other means is operated,the time of the second operation of said first means determining thenature of the incoming line connected with.

5. In an electric selective system in which an outgoing circuit isadapted to be connected with incoming circuits of different characters,a highspeed relay in the outgoing circuit, a second relay, means foroperating the high-speed relay whenever an incoming circuit is connectedwith, means controlled by the operation of said high-speed relay foroperating said second relay, and means for then releasing the high-speedrelay either before or after the said second relay operates dependingupon the character of the incoming circuit connected with.

6. In a selective system, a plurality of lines of different character,test circuits for each line, means in said lines for increasing theimpedance of their test circuits at different times, a selector forconnecting with and testing said lines, a test relay in the selectoroperated when the selector seizes a line, a circuit prepared by saidrelay, another relay controlled by said test relay, means controlled bysaid other relay for opening the prepared circuit, a relay in saidprepared circuit operated when the selector is connected with a linewhich increases its impedance at one time and prevented from operatingby .the operation of said other relay when the selector connects with aline which increases its impedance at a later time.

'7. In a selective system, a plurality of lines, relays of one speed oncertain of said lines and relays of another speed on other of saidlines,

a selector for connecting with and testing said lines, means in theselector for closing a test circuit including the relay of the lineconnected with, means responsive to the operation of the relay of theline for sending a signal back to the selector, means in the selectorconnected for operation for an interval only, and means for operatingsaid last means only when the signal sent back by the relay of aconnected line is of a certain speed.

8. In a telephone system, a plurality of lines of different character, aselector switch for connecting with and testing said lines to determinethe character thereof, a cut-off relay for each line, certain of saidrelays operating at different speeds, a test relay in the selector, acircuit closed when a line is seized including said test relay and thecut-01f relay of the line connected with, said relays operated in saidcircuit, said cut-off relay when operated changing the resistance ofsaid test circuit to temporarily release the test relay and re-energizeit, the release of the test relay being dependent upon the speed ofoperation of the cut-off relay, and means in the selector operated ifthe test relay falls back'at one time and prevented from operating if itfalls back at an earlier time.

HORACE EDGAR HUMPHRIES.

